chanfunding: adds ability to fund up to some maximum amount
Allows to define a maximum amount to provision a channel opening with using a new field `FundUpToMaxAmt` on the `Request` struct. Also adds a new coin select function `CoinSelectUpToAmount` to select coins up to a maximum amount respecting a minimum amount.
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Bjarne Magnussen authored and Slyghtning committed
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@@ -518,15 +518,219 @@ func TestCoinSelectSubtractFees(t *testing.T) {
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}
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}
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// Assert we got the expected change amount.
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// Assert we got the expected funding amount.
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if localFundingAmt != test.expectedFundingAmt {
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t.Fatalf("expected %v local funding amt, got %v",
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test.expectedFundingAmt, localFundingAmt)
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}
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// Assert we got the expected change amount.
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require.EqualValues(
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t, test.expectedChange, changeAmt,
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)
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})
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}
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}
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// TestCoinSelectUpToAmount tests that we pick coins adding up to the
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// expected amount when creating a funding transaction, and that a change
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// output is created only when necessary.
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func TestCoinSelectUpToAmount(t *testing.T) {
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t.Parallel()
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const (
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feeRate = chainfee.SatPerKWeight(100)
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dustLimit = btcutil.Amount(1000)
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dust = btcutil.Amount(100)
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coin = btcutil.SatoshiPerBitcoin
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minValue = 20_000
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)
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type testCase struct {
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name string
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minValue btcutil.Amount
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maxValue btcutil.Amount
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coins []Coin
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expectedInput []btcutil.Amount
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expectedFundingAmt btcutil.Amount
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expectedChange btcutil.Amount
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expectErr string
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}
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testCases := []testCase{{
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// We have 1.0 BTC available, spend them all.
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// This should lead to a funding TX with one output, the rest
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// goes to fees.
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name: "spend exactly all",
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coins: []Coin{{
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TxOut: wire.TxOut{
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PkScript: p2wkhScript,
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Value: 1 * coin,
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},
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}},
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minValue: minValue,
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maxValue: 1 * coin,
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// The one and only input will be selected.
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expectedInput: []btcutil.Amount{1 * coin},
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expectedFundingAmt: 1*coin - fundingFee(feeRate, 1, false),
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expectedChange: 0,
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}, {
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// We have 1.0 BTC available and want to spend up to 2 BTC.
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// This should lead to a funding TX with one output, the rest
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// goes to fees.
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name: "spend more",
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coins: []Coin{{
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TxOut: wire.TxOut{
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PkScript: p2wkhScript,
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Value: 1 * coin,
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},
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}},
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minValue: minValue,
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maxValue: 2 * coin,
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// The one and only input will be selected.
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expectedInput: []btcutil.Amount{1 * coin},
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expectedFundingAmt: 1*coin - fundingFee(feeRate, 1, false),
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expectedChange: 0,
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}, {
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// We have 1.0 BTC available and want to spend up to 0.5 BTC.
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// This should lead to a funding TX with one output and a
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// change to subtract the fees from.
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name: "spend far below",
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coins: []Coin{{
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TxOut: wire.TxOut{
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PkScript: p2wkhScript,
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Value: 1 * coin,
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},
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}},
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minValue: minValue,
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maxValue: 0.5 * coin,
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// The one and only input will be selected.
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expectedInput: []btcutil.Amount{1 * coin},
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expectedFundingAmt: 0.5 * coin,
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expectedChange: 0.5*coin - fundingFee(feeRate, 1, true),
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}, {
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// We have 1.0 BTC available and want to spend just 1 Satoshi
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// below that amount.
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// This should lead to a funding TX with one output where the
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// fee is subtracted from the total 1 BTC input value.
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name: "spend little below",
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coins: []Coin{{
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TxOut: wire.TxOut{
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PkScript: p2wkhScript,
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Value: 1 * coin,
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},
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}},
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minValue: minValue,
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maxValue: 1*coin - 1,
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// The one and only input will be selected.
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expectedInput: []btcutil.Amount{
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1 * coin,
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},
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expectedFundingAmt: 1*coin - fundingFee(feeRate, 1, false),
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expectedChange: 0,
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}, {
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// The total funds available is below the dust limit after
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// paying fees.
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name: "dust output",
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coins: []Coin{{
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TxOut: wire.TxOut{
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PkScript: p2wkhScript,
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Value: int64(
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fundingFee(feeRate, 1, false) + dust,
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),
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},
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}},
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minValue: minValue,
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maxValue: fundingFee(feeRate, 1, false) + dust,
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expectErr: "output amount(0.000001 BTC) after subtracting " +
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"fees(0.00000048 BTC) below dust limit(0.00001 BTC)",
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}, {
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// If more than 20% of available wallet funds goes to fees, it
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// should fail.
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name: "high fee",
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coins: []Coin{{
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TxOut: wire.TxOut{
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PkScript: p2wkhScript,
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Value: int64(
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20 * fundingFee(feeRate, 1, false),
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),
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},
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}},
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minValue: minValue,
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maxValue: 16 * fundingFee(feeRate, 1, false),
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expectErr: "fee 0.00000192 BTC on total output value " +
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"0.00000768 BTC",
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}, {
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// This test makes sure that the implementation detail of using
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// CoinSelect and CoinSelectSubtractFees is done correctly.
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// CoinSelect always defaults to use a fee for single input -
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// one change tx, whereas CoinSelectSubtractFees will use a fee
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// of single input - no change output, which without a sanity
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// check could result in a local amount higher than the maximum
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// amount that was expected.
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name: "sanity check for correct maximum amount",
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coins: []Coin{{
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TxOut: wire.TxOut{
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PkScript: p2wkhScript,
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Value: 1 * coin,
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},
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}},
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minValue: minValue,
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maxValue: 1*coin - fundingFee(feeRate, 1, false) - 1,
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expectedInput: []btcutil.Amount{1 * coin},
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expectedFundingAmt: 1*coin - fundingFee(feeRate, 1, false) - 1,
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expectedChange: 0,
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}}
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for _, test := range testCases {
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test := test
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t.Run(test.name, func(t *testing.T) {
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t.Parallel()
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selected, localFundingAmt, changeAmt,
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err := CoinSelectUpToAmount(
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feeRate, test.minValue, test.maxValue,
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dustLimit, test.coins,
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)
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if len(test.expectErr) == 0 && err != nil {
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t.Fatalf(err.Error())
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}
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if changeAmt != test.expectedChange {
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t.Fatalf("expected %v change amt, got %v",
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test.expectedChange, changeAmt)
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}
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if len(test.expectErr) > 0 && err == nil {
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t.Fatalf("expected error: %v", test.expectErr)
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}
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if len(test.expectErr) > 0 && err != nil {
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require.EqualError(t, err, test.expectErr)
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}
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// Check that the selected inputs match what we expect.
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require.Equal(t, len(test.expectedInput), len(selected))
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for i, coin := range selected {
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require.EqualValues(
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t, test.expectedInput[i], coin.Value,
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)
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}
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// Assert we got the expected funding amount.
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require.Equal(
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t, test.expectedFundingAmt, localFundingAmt,
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)
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// Assert we got the expected change amount.
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require.Equal(
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t, test.expectedChange, changeAmt,
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)
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})
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}
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}
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